Cu(II) harmonize g-C3N4 and black phosphorous together under the interaction of surface charges to form unconventional type-II photocatalyst BPs/Cu/CNs with attractive performance

Abstract

Rational utilization of the surface charge property of components is an effective method to prepare heterojunction. The surface of g-C3N4 nanosheets (CNs) and black phosphorous nanosheets (BPs) both exhibit negative charge, which would produce repulsive force to hinder them from approaching each other. Herein, non-noble and low-toxic Cu(II) was selected to harmonize the CNs and BPs together under the interaction of surface charges, and the Cu(II) was reduced in situ to Cu with good conductivity, obtaining the sandwich-like product BPs/Cu/CNs with tight interface and high separation efficiency of photogenerated carriers. The composites exhibited attractive degradation performance for various pollutants under visible light, especially, 95.3 % of ciprofloxacin (10 mg/L, 200 mL) was removed in 60 min with 50 mg of 6BPs/4Cu/CNs as photocatalyst, and the removal ratio can still reach 87.4 % after the fifth reuse with negligible leaching of Cu ions. An unconventional type-II band structure was built in the BPs/Cu/CNs under the drive of internal electric field and mutual attraction of opposite charges, in which the e- from CB of BPs transferred to Cu and then combined with the h+ from VB of CNs, leaving the e- from CB of CNs and h+ from VB of BPs still work. Despite the same result to that of typical type-II band structure of BPs/CNs, the flow of photogenerated carriers in the BPs/Cu/CNs was more favorable in thermodynamics.